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PRELIMINARY 
APPLE BASIC USERS MANUAL 
OCTOBER 19 76 



Apple Computer Company • 770 Welch Rd., Palo Alto, CA 94304 • (415) 326-4248 



This is a PRELIMINARY manual. It will, most likley, contain 

errors, incorrect wordings, etc. Your effort in noting these 

areas of improvement will be greatly appreciated. 

If you find an error or can suggest an improvement, please 

write: 

APPLE COMPUTER COMPANY 

770 WELCH RD. SUITE 154 

PALO ALTO, CA 94304 

(415) 326-4248 



LOADING APPLE BASIC 

Apple BASIC is provided on a cassette tape which can be read into 
the "E lf block of memory in about 30 seconds. To load BASIC from 
the tape do the following: 

Hit the "CLEAR SCREEN" button which will clear the screen 
and display only the cursor (a flashing @ sign) in the 
upper left corner of the screen. 

Hit the "RESET" button which will cause the computer to print 
a backslash (\) and move the cursor down a line. 

Place the BASIC cassette into the recorder , rewinding it if 

necessary. 

NOTE*** The symbol + means hit the "RETURN" key on the keyboard 

The symbol + will not, of course, be printed on the 

screen. 

1. Type C100R * 

2. Type . EJWf.EFFFR (don't hit + yet!) 

3 . Start the tape 

4. Hit + 

5. When BASIC is loaded (about 30 seconds) the computer will 
print a backslash (\) . 

To enter BASIC type EJ?j2f^R^ . The computer will print a few charac- 
ters, then, on the next line, print the prompt character >. This 
prompt character (>) is used throughout BASIC to signify that the 
BASIC is ready for additional commands or statements. 

To exit BASIC hit the "RESET" button. This will return control 
to the monitor. To re-enter BASIC from the monitor without losing 
the previous program, enter BASIC at E2B3^, instead of EJ3f0j2f+. 
This is extremely useful when you have unintentionally hit the 
"RESET" button while in BASIC. Normally, you should enter BASIC 
at E000+ , which clears any previous programs . 



It is advisable to make a duplicate copy of Apple BASIC on another 
cassette. Exit BASIC as described and: 



1. 


Type 


cipjnu 


2. 


Type 


EJWf.EFFFW (don 1 1 hit + yet!) 


3. 


Start the tape 


(Recording) 


4. 


Hit +. 





5. The computer will print a backslash (\) when finished. 

READING AND WRITING BASIC PROGRAMS ON TAPE 

It is possible to store and retrieve BASIC programs on/from a 
cassette tape. To write a BASIC program onto a tape: 

1. Exit BASIC as described above. 

2 . Type Clj2fj2fR4- 

3. Type 4A.00FFW8j2f0.FFFW (don't hit 4- yet!) 

4. Start the tape (Recording) 

5. Hit K 

6. - The computer will print a backslash (\) when completed. 

7. Enter BASIC at E2B3. 

To read a BASIC program from a tape, the same procedure is used 
except an R (for READ) is substituted for each W in line 3 above 
and the tape unit is playing instead of recording. Loading a 
BASIC program in this manner can be done either prior to loading 
BASIC or any time thereafter by first exiting BASIC, loading the 
program, and re-entering BASIC at E2B3. 

PROGRAM EXECUTION 

To review all of the program statements, the LIST command is 
used. To execute the program the RUN command is used, which 
causes the current program to be executed. Program execution 
may be interrupted by pressing any key. BASIC will then output 
a "STOPPED AT X" message to identify the point of interruption, 
where X is a line number. 



NOTE*** A BASIC program can only be interrupted at the conclusion 
of a line. Therefore, the program: 

10 FOR 1=1 to 10 STEP?: NEXTI 
cannot be interrupted. It is good practice to separate 
potentially erroneous statements onto different lines to 
allow interruption if necessary. 

The user may wish to examine or modify some of the program 
variables before resuming execution of the program. This can be 
done with BASIC commands, which execute immediately. For example, 
after interrupting a program, the commands: 

PRINT A,B,C,D Will print the values of A,B,C and D 
A = 100 Will assign A = 100 

PRINT A$ Will print the string A$ 

To resume execution of a BASIC program after interruption, type: 

GOTO X , where X is the line number in the message 
"STOPPED AT X". GOTO X will begin execution at line number X 
without" re-initializing all variables and strings in contrast to 
RUN, which re-initializes everything. Therefore, you must use 
GOTO X when resuming execution of the program. 

ABBREVIATIONS 

The following abbreviations are used in this manual: 
expr stands for an arithmetic expression. 
var is a variable name (numeric, array, or string), 

val is a number between -32161 and 32767 inclusive. 
+ indicates the pressing of the RETURN key. 



NUMERIC REPRESENTATION 

Apple BASIC can represent integers in the range -32767 to +32767 
Entered values or calculations which result in values outside 
these boundaries will produce the error message ">32767" . 

VARIABLES 



In Apple BASIC the allowed variables and variable names are: 

Variable Name Example 

numeric simple variable letter or A, N 

letter + digit Al, T6 

numeric array variable letter or N, T 

letter + digit Bl, T4 

character string variable letter + $ A$ , N$ 

The same letter may be used to name any or all of the above types 
of variables in one program. 

NOTE*** In Apple BASIC the first element of an array, A(l) is 
identical to the simple variable A. 

EXPRESSIONS 



An expression is a combination of numbers, variables, functions, 
and operators that can be, by calculation, reduced to a single 
value. The simplest expression is a number. Another simple 
expression is a variable name. Simple expressions can be combined 
to make arbitrarily complex expressions. Any expression may be 
enclosed in parentheses. Operations inside a pair of parentheses 
will be performed before any operations outside the parentheses. 

ARITHMETIC AND RELATIONAL OPERATORS 

-expr negative one (-1) times the value of the expr. 

NOT expr if expr is non-zero, 1 if expr is zero. 

expr * expr the product of the two expressions. 

expr / expr the quotient, truncated to an integer, 

expr + expr the sum of the two expressions, 

expr - expr the difference of the two expressions. 



Relational expressions evaluate to one (1) if the condition is met, 
zero (0) if the condition is not met. 



expr - expr 
expr > expr 
expr < expr 
expr >= expr 
expr <= expr 
expr <> expr 
expr # expr 

expr AND expr 
expr OR expr 
expr MOD expr 



1 if expressions are equal* 

1 if first expr greater than second. 

1 if first expr less than second. 

1 if first expr greater than or equal to second. 

1 if first expr less than or equal to second. 

1 if the expr are unequal. 

1 if expr are unequal, same as <> . 

1 if neither expr equals zero. 
1 unless both expr equal zero, 
remainder left after dividing first expr by second 



FUNCTIONS 
ABS (expr) 

SGN(expr) 
PEEK (expr) 

RND(expr) 
LEN(var$) 



has the value of the expr when expr is zero or 
positive, and has the value of (-1 * expr) when 
expr is negative. 

if expr is zero, 1 if expr is positive, -1 if 
expr negative. 

is the value (decimal- between and 255 inclusive) 
of the memory location whose (decimal) address is 
equal to expr. 

if expr is positive - gives a random integer 
between and (expr -1) . 

if expr is negative - gives a random integer 
between and (expr+1) . 

returns the value equal to the number of characters 
currently assigned to the string whose name is var$ 



ARRAYS 

An array is a set of variables (numbers) assigned to a common 

variable name. Each variable of the set is identified by the 

name of the array followed by a parenthesized subscript. For 

example: A (3) references the third variable (number) of the 

array A. Other examples are: A(15) , D(100) , E(X). 

In Apple BASIC, the first element of an array, B(l), is identical 

to the simple variable B. A reference to element zero (0) or a 

negative reference is an error, and will generate the error 

message "RANGE ERR". 

Declaring arrays is done using a DIM statement, which gives the 

name of the array and its DIMensions. 



The DIMension of an array specifies the number of variables in an 
array (the maximum allowable subscript) . For example: 
DIM A (15) , N(6) assigns 15 variables to the array A (A(l) through 
A(15)) and six variables to the array N (N(l) through N(6)). There 
is no limitation on the number of variables dimensioned for an 
array other than restrictions due to available memory. If memory 
limitations are exceeded, a "MEM FULL ERR" will result. 
NOTE*** Array variables are not initialized to any value. 

STRINGS 

Apple BASIC provides the user with the capability to manipulate 
character strings . A string is a sequence of characters which may 
include letters, digits, spaces and special characters (except 
quotation marks) . A string literal (constant) is a string enclosed 
within quotation marks. String literals are often used in PRINT 
and INPUT statements - 

100 PRINT "THIS IS A STRING LITERAL" 

200 INPUT "X=", X 
The quotation marks are not printed with the string. BASIC also 
permits the use of string variables. String values are assigned to 
string variables using the LET (or Implied LET) and INPUT commands. 
Apple BASIC strings function according to the following rules: 

1. String variable names must be of the form: letter $ (Z$) . 

2. A string is DIMensioned for a maximum length using the DIM 
statement of the form: DIM A$(20), B$(100) ... 

A string may be DIMensioned to have a maximum length of from 1 
to 255 inclusive. If an attempt is made to DIMension a string 
outside this range, the error message "RANGE ERR" will result. 

3. If it is not specified in a DIM statement, a string's maximum 
length is taken to be zero (empty) . 

4. A string may contain fewer characters or the same number of 
characters as its maximum length, but may never contain more 
characters than its maximum length. If an attempt is made to 
exceed this maximum length, the error message "STR OVFL ERR" 
(string overflow error) will result. 



SUBSTRINGS 

Program statements using string variables may also use portions 
of strings (substrings) by subscripting the string variable name. 

Where no subscript is specified, the entire string is referenced. 

If one subscript is specified - A$(5) for example - the characters 

occupying the 5th (in this case) through the last position 

inclusive are referenced. 

If two subscripts are specified - A$(2,6) for example - the 

characters occupying the positions 2 through 6 inclusive are 

referenced. 

Any numeric expressions may be used as subscripts. A$(I / J) for 

example, references the characters occupying positions I through 

J inclusive/ where I and J are evaluated to character positions 

in the string and I is less than or equal to J. 

For example, assume that A$="ABCDEFG" , then 
PRINT A$ yields ABCDEFG 
PRINT A$(5) yields EFG 
PRINT A$(2,6) yields BCDEF 
PRINT A$(l,l) yields A 

DESTINGATION STRINGS 

A destingation string is a string variable into which a different 
(source) string is being copied. Part or all of the destination 
string may be replaced by part or all of the source string. 
Rules 

1. The destination string (to the left of the " = " sign) must be 
large enough to hold the source string. 

2. If no subscripts are specified (A$=B$) then the entire source 
string (B$) replaces the entire string in the destination 
variable (A$) . (If the source string is shorter than the 
destination string, trailing blanks are appended as necessary) 

3. If one subscript is specified for the destination string 
(A$(5) = B$) then the destination string, beginning with the 



specified character (the 5th character in this case) is 
replaced with the source string, 

4. Specifying two subscripts (A$(3,5)) for the destination 
string is not allowed in Apple BASIC, 

5. Zero, one or two subscripts may be specified for the source 
string, following the rules listed for substrings. 

LEN FUNCTION 

The LEN function returns the value equal to the number of charac- 
ters currently assigned to a string variable. 
Its form is: LEN(X$) . 

The length function can be used to link strings together as 
follows: B$ (LEN(B$)+1) = A$ . This will assign the characters 
from source string A$ to sequential character positions immediately 
following the last character previously assigned to the destination 
string, B$. The LEN function may be used with any program state- 
ment or command which has an expression (expr) argument. 

STRING IF STATEMENT 

Strings may be used in the relational expression of an IF - THEN 
STATEMENT. The logical operators allowed in Apple BASIC for a 
string IF statement are = and # (equal and not-equal) . The 
strings are compared character by character on the basis of the 
ASCII character value. String variables may be subscripted in 
an IF statement (IF A$(3,7) = B$(4,8) THEN ...). If characters 
in the same positions are identical but one string has more 
characters than the other, the strings are considered not-equal. 



BASIC INSTRUCTIONS 

There are two kinds of instructions in BASIC: Commands and State- 
ments. Commands are executed immediately after a + , do not have 
line numbers, and are not part of a program. Statements are 
always preceded by line numbers and become part of a program. 
Statements are executed only during the execution of a program. 

Several BASIC instructions can be used both as statements and as 
commands . When used as commands , they execute immediately and 
are not part of a BASIC program. Used in this manner they can 
be useful for immediately examining or modifying program variables 
during interruption of program execution. With this feature, the 
Apple computer is also a simple calculator able to perform 
mathematical calculations immediately, without the necessity of 
writing a program. An instruction used as both a statement and 
a command: 

>10 PRINT A,B This is a statement in a BASIC program. Upon 

encountering line 10, a BASIC program will 
print the values of variables A and B. 

>PRINT A,B This is a command. The current values of A 

and B will be printed immediately after a +. 

COMMANDS 

The following commands (control commands) are used to enter, 
examine, modify and run BASIC programs. In addition to the con- 
trol commands several BASIC instructions which can be used as 
commands are denoted in the list of statements. 

AUTO vail, vail starts automatically supplying line numbers. 

vail specifies the first line number value 
and val2 specifies the increment between 
successive line number values. If val2 is 
omitted, it is assumed to be ten (10) . 
A control D (hitting the control key and D 
simultaneously) will terminate AUTO. 

CLR sets all variables to zero, cancels any 

pending FORs or GOSUBs and undimensions any 
array and string variables. 



DEL vail, val2 



LIST vail, val2 



RUN vail 



SCR 

HIMEM = (expr) 

LOMEM = (expr) 



erases from the program all lines numbered 
from vail to val2 inclusive. If val2 is 
omitted , just one line (vail) is DELeted. 

displays all program statements on lines 
numbered from vail to val2. If val2 is 
omitted, just line vail is displayed. If 
both vail and val2 are omitted, the entire 
program is LISTed. 

does a CLR then initiates program execution 
beginning at line vail* If vail is omitted, 
then program execution starts at the lowest 
numbered line. 

SCRatches (DELetes) the entire program. 
Nothing is saved. 

sets the high memory boundary for user pro- 
grams (in decimal) . Initializes to 4096. 

sets the low memory boundary for user pro- 
grams (in decimal). Initializes to 2048. 
Both HIMEM and LOMEM destroy any current 
user programs. 



STATEMENTS 

Those BASIC instructions that can also be used as commands are 
denoted with a "C" in the left margin. 

C LET vav - expr or var = expr (Implied LET) 

LET evaluates expr and asigns the resultant value to 
vav. Use of the word LET is optional. Variables may 
be of any type (string, array, numeric) . 

INPUT item 

An item may be any kind of variable name (string, array, 
numeric) . An INPUT statement may contain several items 
separated with commas, each of which must be supplied a 
value. 

INPUT prints a question mark (?) and awaits the user to 
input a value for the variable. A message can be printed 
prior to the "?" by preceding the list of variables by a 
message (in quotation marks) followed by a comma. 
Responses to a multi -variable INPUT statement must be 
separated, using either a comma or a \ between each 
response. If an INPUT statement contains one or more 



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string variables, the responses must be separated with a 
+ (commas not allowed) . 

Examples: INPUT A 

INPUT A,B,C$,D(2) 

INPUT "ENTER A, A$ ,8(3) " , A,A$,B(3) 

C PRINT item(s) 

The item may be any kind of variable name, an expression, 
or a message to be printed. A message must be enclosed 
in quotes. 

Any number of items may be printed using one PRINT state- 
ment. The items must be separated by either semicolons 
(;) or commas (,). The semicolon indicates that the items 
are to be printed with no intervening space. The comma 
forces the item following it to be printed in the next 
available column position. For this purpose the screen 
is thought of as consisting of five columns each eight 
characters wide. 

A semicolon at the end of a list of items indicates that 
tile next PRINT statement to be executed will begin print- 
ing exactly where the present one stopped. A terminating 
comma is illegal. 

Examples: PRINT A,C$,D(2) 

PRINT "message" ;A,; "message" ; 
PRINT •"A$=";A$;" — END" 

C TAB (expr) 

Prints the number of spaces equal to the value of expr 
(Modulo 256) . 

Examples: TAB 20: PRINT "Hello" 
PRINT A;: TAB 20:PRINT B 

FOR var = exprl TO expr2 STEP expr3 

NEXT var 

The FOR and NEXT statements form a pair. The FOR state- 
ment sets a numeric variable (var) equal to the value of 
exprl. Execution proceeds until the statement NEXT var 
occurs. At that time if var exceeds the value of expr2 
execution continues from the statement following the NEXT 
var. If var does not exceed the value of expr 2 then the 
value of expr3 s is added to var and execution proceeds 
from the statement following the FOR. If STEP expr3 is 
omitted from the FOR statement, then expr 3 is assumed to 
be +1. 

Examples: FOR 1= 1 TO 100 

' FOR A= 100 TO 1 STEP -5 
NEXT I 
NEXT I, J 



11 



C IF (expr) THEN statement IF (expr) THEN line number 

If the value of the expression is zero no further action 
is taken and execution continues with the next statement 
following the IF statement. When the value of the 
expression is one (1) the statement following THEN is 
executed. A line number may also follow a THEN (instead 
of a statement) . This instruction can be used as a com- 
mand only if the instructions following THEN are also 
commands . 

Examples: IF A=B THEN C=l 

IF (A=B AND C=D) THEN 50 
IF NOT (A>4) THEN END 

C GOTO expr 

GOTO branches to the line number which equals expr. 

Examples: GOTO 100 
GOTO A 
GOTO (A+B/2) 

GOSUB expr 
RETURN 

GOSUB and RETURN form a pair. GOSUB branches to the line 
number which equals expr. RETURN causes a branch to the 
line following the most recently executed GOSUB. There 
may be several conditional RETURNS in a GOSUB loop. 

Examples: GOSUB 100 
GOSUB A 
RETURN 

C DIM varl (exprl) , var2 (expr2) ... 

DIMensions an array or string named varl to the value 
of exprl, an array or string named varl to the value 
of expr 2, and so on. String and numeric variables may 
be mixed. An array or string may only be DIMensioned 
once in a program. 

Examples: DIM A (100) 

DIM A$(20) ,B$(10) ,C(50) 

C REM text 

REMark lets the user insert comments in a program without 
affecting the execution of the program. The comments 
immediately follow the REM statement and are preserved 
literally (spaces and all) . REMarks are printed when 
listing the program. 

Example: REM THIS IS A REMARK 



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END 

END stops execution of the program. 

POKE exprl, expr2 

Puts the value of expr2 (decimal- must be between zero 
and 255 inclusive) into the memory location (decimal) 
whose value is equal to exprl. 

Examples: POKE 4,64 stores 64 in location 4 

POKE -2048,55 stores 55 in location -2048 



(-2048 = D000 (HEX)) 



CALL expr 



CALL does a JSR to the memory location whose address is 
equal to the value of the expr (decimal) . This state- 
ment links BASIC with assembly language s ub routine s . 
An assembly language RTS (return from subroutine) will 
return control to the BASIC and execute the next state- 
ment. 

Examples: CALL 64 
CALL A 



NOTE*** Apple BASIC allows putting several statements on one 

line number. Each statement must be separated using a 
colon ( :) . 



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APPLE BASIC ERROR MESSAGES 



*** SYNTAX 
*** > 32767 ERR 

*** >255 ERR 

*** BAD BRANCH ERR 

*** BAD RETURN ERR 

*** BAD NEXT ERR 

*** >8 GOSUBS ERR 
*** >8 FORS ERR 
*** END ERR 
*** MEM FULL ERR 

*** TOO LONG ERR 
*** DIM ERR 

*** RANGE ERR 
*** STR OVFL ERR 

*** STRING ERR 
RETYPE LINE 



Results from a syntactic or typing error. 

A value entered or calculated was less 
than -32767 or greater than 32767 • 

A value restricted to the range to 255 
was outside that range. 

Results from an attempt to branch to a 
non-existant line number. 

Results from an attempt to execute more 
RETURNS than previously executed GOSUBs. 

Results from an attempt to execute a NEXT 
statement for which there was not a 
corresponding FOR statement. 

Results from more than 8 nested GOSUBs. 

Results from more than 8 nested FOR loops. 

The last statement executed was not an END. 

The memory needed for the program has 
exceeded the memory size allotted. 

Results from too many nested parentheses. 

Results from an attempt to DIMension a 
string array which has been previously 
dimensioned. 

An array or string subscript was larger than 
the DIMensioned value or smaller than 1. 

The number of characters assigned to a 
string exceeded the DIMensioned value for 
that string. 

Results from an attempt to execute an 
illegal string operation. 

Results from illegal data being typed in 
response to an INPUT statement. This message 
also requests that the illegal item be 
retyped. 

A backslash results when more than 128 
consecutive characters are entered without 
an intervening 4- . 



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